Generally, a radio receiver includes various analog circuits. Recently, in the radio receiver, a technology for replacing some of analog circuits with digital circuits is employed for the purpose of higher performance and miniaturization.
Conventionally, a function of correcting a deviation (IQ imbalance) between an in-phase component and a quadrature component of a radio signal, which is one of functions of the radio receiver, is implemented by the digital circuit. When receiving the radio signal, the digital circuit refers to a well-known portion of the radio signal, estimates an imbalance amount based on the referred portion (reference signal), and corrects the IQ imbalance based on the estimated imbalance amount.
However, in the radio signal, there is not only the IQ imbalance of the radio receiver, but also there are incomplete factors such as an IQ imbalance of a radio transmitter that transmits the radio signal and a communication distortion. Furthermore, the reference signal exists only in a limited frequency of the radio signal. Accordingly, correction accuracy of the imbalance amount is low.
On the other hand, there is a technology for providing a reference signal generator with the radio receiver in order to improve the correction accuracy of the imbalance amount. However, a circuit size and production cost of the radio receiver are increased by the reference signal generator.